1. Technical Field
The present invention relates to a projection type image display apparatus, and specifically, to a thin projection type image display apparatus having a shallow depth.
2. Background
In a projection type image display apparatus, an optical engine makes light from a light source with information into image light. Then, the image light is reflected by a folding mirror and is projected on a screen, and an image is displayed on the screen. In order to prevent a distortion or a blur of the image, it is necessary to keep relative angle deviations between the optical engine, the screen and the folding mirror with high precision. Specifically, in order to suppress a deformation of the folding mirror, the mirror is thickened or a rigid reinforcement member is attached on a periphery or backside of the mirror.
In addition, in order to make the projection type image display apparatus in a thin type, a ratio of an apparatus height to a depth from the screen to a rear end of the folding mirror is made to be a ratio of 10 to 3, for example, so that an angle between a projection direction to the folding mirror and a horizontal direction is made to be highly great (a projection angle is highly great). In this configuration, a slight deformation of the folding mirror arranged adjacent to a top surface of the apparatus and a relative positional deviation to the screen cause a distortion or a blur in the displayed image projected on the screen. Accordingly, the related rear projection display apparatus has a rigid frame structure for increasing a rigidity and a configuration for easily enabling angle adjustment of the folding mirror after the moving such as delivery (for example, refer to JP-A-2007-183301 (pages 6 to 10 and FIGS. 9 to 11 and 19)).